1. Technical Field
The present invention relates to a connecting terminal for establishing electrical connection between conductor portions of printed circuit boards disposed in a facing relation, and relates to a connecting terminal assembly comprised of a plurality of connecting terminals that are removably attached to a mount base and adapted to be mounted on printed circuit boards with use of an automatic loader.
2. Related Arts
Electronic equipment, such as personal computers and telephone sets, accommodates therein a large number of electronic component parts. Typically, these components parts are mounted on a plurality of printed circuit boards that are accommodated in a cabinet of the electronic equipment. To reduce a space required for installation of the printed circuit boards in the cabinet and to facilitate easy assembly, these circuit boards are disposed in the cabinet in a facing relation to one another. In order to establish electric connection between conductive patterns respectively formed in adjacent printed circuit boards, connecting terminals, such as one disclosed in Japanese provisional patent publication no. 9-115574, have been employed.
This conventional connecting terminal is comprised of a U-shaped metal plate fabricated by bending an elongated plate, punched out from a metal sheet having upper and lower surfaces thereof plated in advance, into a U-shape, as shown in FIG. 9. The connecting terminal, having a first contact section 51 thereof formed by a longer half of the U-shaped plate, is adapted to be soldered at this contact section 51 to a conductor pattern (not shown) of a first printed circuit board 53. To this end, a first and second soldered-connection portions 51a, 51b are formed in the contact section 51 by cutting and upwardly raising a longitudinally intermediate portion and an outer end portion of the contact section 51. These soldered-connection portions 51a, 51b of the connecting terminal 50 are soldered to the conductor pattern of the first printed circuit board 53, whereby the connecting terminal 50 is electrically and mechanically connected to the conductor pattern of the printed circuit board 53. Subsequently, a second contact section 52, formed by a shorter half of the U-shape plate, of the connecting terminal 50 is abutted against a conductor pattern formed in a second printed circuit board 54, so as to be electrically connected thereto. In this manner, electrical connection between the conductor patterns of the first and second circuit boards 53, 54 is established through the connecting terminal 50 having the first fixed-contact section 51 and the second free-contact section 52 elastically flexible relative to the contact section 51.
To ensure that the connecting terminal 50 is properly joined to the printed circuit board 53, with an intended orientation and at an intended position thereon, the soldered-connection portions 51a, 51b of the connecting terminal 50 must be separated at a distance from each other and soldering flux or paste must be applied to surface areas of the conductor pattern of the first printed circuit board 53 that are apart from each other at a distance corresponding to the distance between the soldered-connection portions 51a, 51b. This requirement must be satisfied, especially when the connecting terminal 50 is soldered to the printed circuit board 53 in term of reflowing-type soldering.
If the soldering-flux applied areas of the printed circuit board 53 are not separated at a required distance but form a single area wide enough to cover a longitudinal zone including lengthwise portions of the circuit board 53 which respectively correspond to the soldered-connection portions 51a, 51b of the connecting terminal 50, molten solder flows into between the opposed flat surfaces of the first contact section 51 of the connecting terminal 50 and the printed circuit board 53 during the soldering process in term of reflowing-type soldering or the like. As a result, the connecting terminal 50 may be in a floated state on the molten solder, since the circuit-board-side surface of the first contact section 51 is formed, as a whole, into a single flat plane. In such a floated state, the connecting terminal 50 can be directed to an unexpected orientation, and thus the connecting terminal 50 is sometimes joined, with an undesired orientation, to the printed circuit board 53 after the solder is solidified.
In surface-mounting the connecting terminal 50 to the printed circuit board 53, a suction pickup device is often employed to pick up the connecting terminal by suction and transport the same to the circuit board. In this case, an upper face of the first contact section 51 of the connecting terminal 50 serves as a pickup face to which a suction nozzle of the pickup device is positioned. At the time of picking up the connecting terminal 50, a movable part, including the suction nozzle, of the suction device is moved toward the connecting terminal 50 to permit the suction nozzle to be positioned to the pickup face. To avoid interference between the connecting terminal 50 and the movable part of the pickup device moved toward the connecting terminal 50, the second contact section 52 of the connecting terminal, extending upward from the first contact section 51 toward the suction device, is bent at its proximal end so as to extend at an acute angle with respect to the first contact section 51.
As the acute angle formed between the first and second contact sections 51, 52 becomes small, the vertical dimension of the connecting terminal 50 becomes smaller. In order to electrically connect the circuit boards through such a low-profile connecting terminal 50, the printed circuit boards must be disposed close to each other at a small distance. In other words, electric connection between the printed circuit boards cannot be established with use of the connecting terminal 50, if one or more electric component parts, having a height greater than that of the connecting terminal 50, are mounted to either one or both of the printed circuit boards.
Since the second contact section 52 of the connecting terminal 50 extends at an acute angle with respect to the first contact section 51, the second contact section 52 can be flexed insufficiently in the vertical direction of the connecting terminal 50 when the second printed circuit board 54 is brought in urged contact with the second contact section 52. In this case, a contact force large enough to eliminate a layer of oxide film or the like, if any, on the conductor pattern cannot be produced between a conductor patter 54p of the printed circuit board 54 and the second contact section 52, so that defective electric connection may be caused between the printed circuit board 54 and the second contact section 52.
Furthermore, the conventional connecting terminal 50 can be unsatisfactorily sucked by the suction pickup nozzle so that it may drop therefrom during the picking-up and transfer processes, since the center of the pickup face of the first contact section 51 is deviated from the center of gravity of the connecting terminal 50 whose first contact section 51 is provided at only one end with the second contact section 52.